'\" te
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.TH DDI_DMA_ALLOC_HANDLE 9F "July 13, 2024"
.SH NAME
ddi_dma_alloc_handle \- allocate DMA handle
.SH SYNOPSIS
.nf
#include <sys/ddi.h>
#include <sys/sunddi.h>



\fBint\fR \fBddi_dma_alloc_handle\fR(\fBdev_info_t *\fR\fIdip\fR, \fBconst ddi_dma_attr_t *\fR\fIattr\fR,
     \fBint  (*\fR\fIcallback\fR) (caddr_t), \fBcaddr_t\fR \fIarg\fR, \fBddi_dma_handle_t *\fR\fIhandlep\fR);
.fi

.SH INTERFACE LEVEL
illumos DDI specific (illumos DDI).
.SH PARAMETERS
.ne 2
.na
\fB\fIdip\fR\fR
.ad
.RS 12n
Pointer to the device's  \fBdev_info\fR structure.
.RE

.sp
.ne 2
.na
\fB\fIattr\fR\fR
.ad
.RS 12n
Pointer to a  \fBDMA\fR attribute structure for this device (see
\fBddi_dma_attr\fR(9S)).
.RE

.sp
.ne 2
.na
\fB\fIcallback\fR\fR
.ad
.RS 12n
The address of a function to call back later if resources aren't available now.
The following special function addresses may also be used.
.sp
.ne 2
.na
\fB\fBDDI_DMA_SLEEP\fR\fR
.ad
.RS 20n
Wait until resources are available.
.RE

.sp
.ne 2
.na
\fB\fBDDI_DMA_DONTWAIT\fR\fR
.ad
.RS 20n
Do not wait until resources are available and do not schedule a callback.
.RE

.RE

.sp
.ne 2
.na
\fB\fIarg\fR\fR
.ad
.RS 12n
Argument to be passed to a callback function, if such a function is specified.
.RE

.sp
.ne 2
.na
\fB\fIhandlep\fR\fR
.ad
.RS 12n
Pointer to the  \fBDMA\fR handle to be initialized.
.RE

.SH DESCRIPTION
\fBddi_dma_alloc_handle()\fR allocates a new  \fBDMA\fR handle. A  \fBDMA\fR
handle is an opaque object used as a reference to subsequently allocated
\fBDMA\fR resources.   \fBddi_dma_alloc_handle()\fR accepts as parameters the
device information referred to by  \fIdip\fR and the device's  \fBDMA\fR
attributes described by a \fBddi_dma_attr\fR(9S) structure. A successful call
to \fBddi_dma_alloc_handle()\fR fills in the value pointed to by
\fIhandlep\fR. A  \fBDMA\fR handle must only be used by the device for which it
was allocated and is only valid for one  I/O transaction at a time.
.sp
.LP
The callback function, \fIcallback\fR, indicates how a caller wants to handle
the possibility of resources not being available. If  \fIcallback\fR is set to
\fBDDI_DMA_DONTWAIT\fR, then the caller does not care if the allocation fails,
and can handle an allocation failure appropriately. If  \fIcallback\fR is set
to  \fBDDI_DMA_SLEEP\fR, then the caller wishes to have the allocation routines
wait for resources to become available. If any other value is set, and a
\fBDMA\fR resource allocation fails, this value is assumed to be a function to
call at a later time when resources may become available. When the specified
function is called, it is passed \fIarg\fR as an argument. The specified
callback function must return either \fBDDI_DMA_CALLBACK_RUNOUT\fR or
\fBDDI_DMA_CALLBACK_DONE\fR. \fBDDI_DMA_CALLBACK_RUNOUT\fR indicates that the
callback routine attempted to allocate \fBDMA\fR resources but failed to do so,
in which case the callback function is put back on a list to be called again
later.  \fBDDI_DMA_CALLBACK_DONE\fR indicates either success at allocating
\fBDMA\fR resources or the driver no longer wishes to retry.
.sp
.LP
The callback function is called in interrupt context. Therefore, only system
functions that are accessible from interrupt context  is available. The
callback function must take whatever steps necessary to protect its critical
resources, data structures, queues, and so forth.
.sp
.LP
When a  \fBDMA\fR handle is no longer needed, \fBddi_dma_free_handle\fR(9F)
must be called to free the handle.
.SH RETURN VALUES
\fBddi_dma_alloc_handle()\fR returns:
.sp
.ne 2
.na
\fB\fBDDI_SUCCESS\fR\fR
.ad
.RS 23n
Successfully allocated a new \fBDMA\fR handle.
.RE

.sp
.ne 2
.na
\fB\fBDDI_DMA_BADATTR\fR\fR
.ad
.RS 23n
The attributes specified in the \fBddi_dma_attr\fR(9S) structure make it
impossible for the system to allocate potential  \fBDMA\fR resources.
.RE

.sp
.ne 2
.na
\fB\fBDDI_DMA_NORESOURCES\fR\fR
.ad
.RS 23n
No resources are available.
.RE

.SH CONTEXT
\fBddi_dma_alloc_handle()\fR can be called from user, kernel, or interrupt
context, except when \fIcallback\fR is set to  \fBDDI_DMA_SLEEP\fR, in which
case it can be called from user or kernel context only.
.SH SEE ALSO
.BR ddi_dma_addr_bind_handle (9F),
.BR ddi_dma_buf_bind_handle (9F),
.BR ddi_dma_burstsizes (9F),
.BR ddi_dma_free_handle (9F),
.BR ddi_dma_unbind_handle (9F),
.BR ddi_dma_attr (9S)
.sp
.LP
\fIWriting Device Drivers\fR